The present invention relates to novel piperidinyl sulfone derivatives containing a 2,2,6,6-tetramethylpiperidinyl-4-sulfonyl group which derivatives are useful for preventing ultraviolet light induced degradation of polymers.
Polyolefin resins, such as polyethylene and polypropylene, have long been used in the manufacture of foils, films, fibers, and molded articles. Because of their excellent structural properties, e.g., tensile strength, dimensional stability, etc., the manufactured materials have been extensively used in the construction trades. When used outdoors, however, these materials are continuously exposed to sunlight and UV radiation, which causes severe deterioration of the polyolefin resin, as evidenced by surface cracking, loss of tensile strength and discoloration.
Sterically hindered amines such as the tetramethyl piperidine type are known to stabilize polymers, especially polyolefins such as polypropylene and polyethylene, against degradation caused by UV radiation. Generally speaking, however, it is extremely difficult to predict the degree or extent to which a given hindered amine will protect polyolefins from UV light, since their performance depends upon a number of factors. Some otherwise useful hindered amines have a tendency to exude from polyolefin resins after incorporation, or decompose or evaporate during processing or thereafter, thus, leaving the resin inadequately protected against photodegradation. In addition, some of these hindered amines are also relatively soluble in water and organic solvents and, therefore, can be readily removed from the plastic matrix.
For the above reasons the prior art hindered amine stabilizers are not completely satisfactory and substantial research in this area is continuing. In recent years there have been repeated descriptions in patents (e.g., U.S. Pat. Nos. 4,435,555; 4,366,277; 4,340,534; 4,110,305; 4,107,139; 4,046,736; etc.) on improved hindered-amine stabilizers. A few of these compositions are sulfur-containing; however, none are commercially useful due to excessive odor and performance which is lower than that of similar non-sulfur containing compositions.
Randell, et al., U.S. Pat. No. 3,939,170, disclosed sulfides, sulfoxides, and sulfones having the formula: ##STR2## where X is S, SO, or SO.sub.2 and Y and Y' are the same or different and each is H, OH, O or a straight- or branched-alkyl residue having from one to four carbon atoms, and salts thereof where Y and Y' are other than O. Mayer, et al., Ger. Offen. No. 2,513,607, disclosed dehydropiperidine sulfides and their salts having the formula: ##STR3## where R.sub.1 can be H, OH, or a hydrocarbon group; R.sub.2, R.sub.3, and R.sub.4 can be hydrocarbons and H--X can be phosphorous-, phosphoric-, an aliphatic sulfonic-, or phosphonic acid.